The invention generally relates to a method for radio frequency (RF) dead zone data collection in a wireless network and, more particularly, to a method for RF dead zone data collection using one or more mobile stations (MSs) and will be described with particular reference thereto. However, it is to be appreciated that the invention is also amenable to other applications.
In general, wireless service providers seek to maximize usage of their wireless networks, provide uninterrupted wireless service for subscribers, and keep the cost of providing these wireless services to a minimum. There are often tradeoffs involved between the first two goals and the third. One aspect of wireless communications where the tension between these goals may be seen is in RF coverage trouble spots (e.g., RF dead zones) within cells in the wireless network. For example, one of the causes of lost revenues for the wireless service provider is dropped calls due to RF dead zones.
The geographic region served by a wireless network is divided into a plurality of areas known as “cells”. Typically, each cell includes a base station (BS) that provides an RF interface to MSs in the cell. When the geographic region is first divided into cells, the cells are engineered to provide coverage for the anticipated MS usage. Further, the cell is engineered to take into account topological aspects of its sub-region, such as tall buildings, highway traffic and geological formations such as mountains.
Only when the wireless network is placed into service is the accuracy of the engineering assumptions tested. There may be dead zones that were unanticipated or that develop due to changes in season or new constructions. The wireless service provider may receive complaints regarding dropped calls or no responses from the wireless system. Subscriber complaints may be evaluated by wireless service providers to identify RF dead zones and evaluate the impact of the dead zone on revenue. However, this is not reliable for evaluating the impact on revenue because often a subscriber experiencing a dropped call does not call the wireless service provider's customer service office to complain. Typically, it is more important for the subscriber to call the dropped party back. Later, it is inconvenient and much less important to call customer service with a complaint about the RF dead zone.
Nevertheless, in response to complaints, the wireless service provider then may send out specially equipped trucks to determine the location and extent of the problems. In some cases, the wireless service provider adds repeaters or supplemental “micro” or “pico” cells to provide RF coverage in the dead zones. In many cases, however, additional micro cells to improve RF coverage are frequently over engineered and one (or more) of the micro cells end up lightly loaded. The wireless service provider has thus unnecessarily increased cost while providing modestly improved wireless service.
In addition to responding to complaints, wireless service providers may perform RF drive testing in order to identify these “dead zones” in their service areas. This type of drive testing is an expensive operating cost to the wireless service provider and often needs to be repeated with the change of seasons, when some buildings and structures are constructed, and when other environmental changes causing new or altered dead zones occur. Moreover, many RF dead zones identified through drive testing have little or no impact on revenue to the wireless service provider. The point being that RF drive testing has no way of prioritizing or evaluating the impact of an RF dead zone on revenue.
One approach to solving this problem is disclosed in U.S. Pat. No. 6,459,695 to Schmitt and assigned to Lucent Technologies. The '695 patent discloses a method that rapidly and precisely determines the geographical location of areas of high concentration of usage (hot spots) and areas of poor RF frequency reception (dead spots) by measuring the number of failed call attempts, dropped calls and the like. The method also compares these areas. The identification of an MS and its location are recorded at selected points during a call. If a high number of uncompleted calls or dropped calls are recorded, then the BS can use the last known location of the MSs involved to circumscribe an area in which the hot spot or dead spot occurs. Notably, Schmitt collects location information from MSs during connected calls and stores the location information for any connected call that is subsequently dropped. The stored location information may then be used to identify, for example, RF dead zones.
A similar problem and solution associated with optimizing RF coverage in a wireless network is disclosed in U.S. Pat. No. 6,522,888 to Garceran et al. and assigned to Lucent Technologies. The '888 patent discloses a system for determining coverage in a wireless network that uses location information for an MS and collects information on communications between the MS and the wireless network in association with the location information. The wireless network determines and/or receives location information for the MS along with other information associated with the location information. The information by location can be used to represent the coverage of a geographic region. For example, during communications between a serving BS and an MS, the serving BS could receive and/or determine signal quality measurements of a forward link and/or of a reverse link at a particular location. Additionally, neighboring BSs can monitor the communications and determine and/or receive location information for the location of the MS along with the information associated with or corresponding to the location of the MS. The associated information can be linked with additional parameters, such as MS type, MS identity, frequency, operating conditions and/or BS identity. Notably, Garceran collects location information and various other parameters from MSs and produces an RF coverage map. Depending upon the position of an MS within the RF coverage map, RF transmissions from the MS are adjusted to improve RF coverage. The location information is not used to identify RF dead zones.
Thus, there is motivation for an improved method for collection of data to identify RF dead zones in a wireless network using mobile stations operated by subscribers associated with the wireless network. Moreover, there is a particular motivation to extend the use of data associated with RF dead zones to subsequent reduction or elimination of one or more areas identified as dead zones.